Seat frame assembly for a motor vehicle

ABSTRACT

A seat frame assembly for a motor vehicle comprises a seat frame and a seat back frame. The seat frame and seat back frame are adapted to have cushions mounted thereon. At least one of the vertical support portions is formed from a pair of telescoping tubular blanks including an elongated inner metal blank formed into an integrally formed vertical member extending from a lower portion of the seat back frame to an upper end of the seat back frame and a relatively shorter outer metal blank formed into a sleeve rigidly secured in surrounding relation to the lower portion of the vertical support member. The outer and inner blanks are formed into the sleeve and the vertical member respectively during a hydroforming process in which the inner blank is expanded so that an outer surface thereof is moved into peripheral contact with an inner surface of the outer blank and the inner blank and the outer blank are expanded into peripheral contact with die surfaces defining the exterior surfaces of the one vertical support portion.

BACKGROUND OF THE INVENTION

The present invention relates to seat frame assemblies for motorvehicles and a method for forming the same.

In a typical motor vehicle, the vehicle seats are constructed with ametal seat frame assembly, including a seat back frame and seat frame,and a seat back cushion and seat cushion mounted in overlying relationon the seat back frame and seat frame, respectively. The seat back framehas lower portions thereof operatively connected with rearward portionsof a metal seat frame. The seat frame can be of several differentconfigurations, such as the cross-wire type in which a plurality ofparallel and/or diagonal metal cross wires are interconnected betweensupport brackets formed into a substantially rectangular configuration,and the pan type in which a shallow rectangular pan is mounted onsupport brackets. Seat back frames, on the other hand, typically includea pair of spaced vertical support portions defining opposite sidesthereof and rigid horizontal support members interconnectedtherebetween. The seat back frames also may include theparallel/diagonal cross wires.

The connection between the seat back frame and seat frame is usuallyformed with a reclining mechanism that is capable of permitting the seatback frame to be pivotally movable with respect to the seat frame so asto enable a seat occupant to adjust the angle at which the seat backcushion is reclined with respect to the seat cushion for maximizedcomfort. Because the reclining mechanism connects the rearward portionof the seat frame with the lower portion of the vertical supports of theseat back frame, it can be appreciated that the lower portion of thespaced vertical supports are particularly subjected to large amounts ofmechanical stresses, especially when the seat back is reclined at largeangles with respect to the seat, and even more so when an individualoccupies the seat.

While it is important to manufacture the vehicle seat frame assemblywith sufficient strength, it is equally important that the frameassembly not be made from excessive amounts of metal, otherwise materialcosts and vehicle weight will be unnecessarily high. Thus, for the mostpart, the vertical support portions and cross members of the seat backframe are hollow (tubular) in form. To accommodate for theaforementioned mechanical stresses, however, it has been known tomanufacture at least one of the spaced vertical supports with arelatively large wall thickness, cross sectional diameter and strength.It is especially important for the lower portion of the heavier verticalsupport, where the majority of the stress is encountered, to be ofsuperior strength. While it is possible for both vertical supportportions to be of the heavier construction (and is actually preferred ina bench seat configuration), sufficient strength for a single occupantseat (such as a bucket seat) is accomplished with only one of thevertical supports manufactured in such fashion. Providing only one ofthe vertical supports with a heavier construction is advantageousbecause less metal, without compromising frame strength.

The heavier vertical support portion (or "main vertical support") isalso advantageous because it enables the frame to mount a vehicle seatbelt. More specifically, in certain vehicles, it may be desirable tomount a seat belt assemblies directly to the seat, as opposed to thevehicle floor. To accomplish this, however, it is necessary tomanufacture the seat frame with sufficient rigidity and strength towithstand the inertial forces encountered in a collision. With the heavyvertical support member, a shoulder belt guide can be mounted on anupper end thereof without the potential for buckling of the mainvertical support member in a collision. A belt reel can then be mountedat a rearward portion of the seat frame in proximity to the lowerportion of the main vertical support member. The belt extends upwardlybehind the seat back frame and through the shoulder belt guide forwardlyof the seat back frame, and then downwardly until it terminates at ananchor fixed to the rearward side of the seat frame, adjacent thereclining mechanism. A belt clasp is slidingly disposed on a portion ofthe belt between the belt guide and the anchor. A separate belt memberis anchored at a side of the seat frame opposite the recliningmechanism, and terminates at a belt latch fixed thereto. A seat occupantcan then easily grasp the belt clasp on the shoulder belt and bring itover his or her shoulder, diagonally across the chest and into latchingengagement with the belt latch. With the shoulder belt guide mounted onan upper corner portion of the seat back frame, it can be appreciatedthat, upon a collision, the main vertical support mounting the shoulderbelt guide is once again subjected to a great amount of mechanicalstress, especially towards the lower portion thereof.

In producing the main vertical support, manufacturers conventionallyemploy a stamping technique. Stamping is accomplished by utilizing oneor more opposing stamping die members which compress (by impact) a sheetof raw steel therebetween into a desired configuration. To manufacturethe main vertical support by stamping, two separate longitudinal sheetsof material are individually stamped into a C-shaped transversecross-section configuration, and then seam welded in facing relationinto a tubular configuration.

While it may be desirable to manufacture a main vertical support whichis straight, the more usual situation requires the main vertical supportto be somewhat bent to accommodate the desired shape of the seat. Thus,after assembly into an elongated tubular configuration, the mainvertical support may be bent in a bending mill as required.Alternatively, the individual C-sections may be stamped into aparticular shapes that will provide the desired bends when assembledinto the final main vertical support.

The stamping process is relatively slow, as it requires raw material tobe stamped, then seam welded into tubular elongated form, and thenoptionally bent. In addition, the process is relatively expensive, asstamping dies and equipment are costly and must be replaced on afrequent basis. Another problem associated with stamping a straightmetal sheet is that a significant amount of raw material is oftenwasted, especially where irregularly shaped frame parts are required.More specifically, where irregular shapes are to be stamped from a sheetof raw metal, there is a significant amount of peripheral material atthe side edges of the sheet that cannot be used, irrespective of howclosely the stamped shapes are nested on the sheet. In one analysis, itwas found that up to 30% of a roll of raw material could not be used dueto the irregular shape of the stamped part. It can be appreciated that,at high volumes, the amount of material wasted, and costs associatedtherewith, is significant in the stamping method. It can also beappreciated that labor, material, and equipment costs associated withmanufacturing and assembly of stamped frame members is significant.

In recent years, a hydroforming procedure has been used to replacestamping for certain applications. For example, hydroforming is proposedas a preferred method of forming a vehicle siderail frame assembly incopending U.S. patent application No. 08/314,496. Hydroforming utilizesfluid pressure applied internally to a tubular blank to expand the blankinto an irregular shape. More particularly, the tubular blank is placedinto a hydroforming mold, and water pressure of up to 10,000atmospheres, and possibly even greater, is provided interiorly to theblank as opposite ends of the blank are pushed inwardly to obtainmaterial flow. The tubular blank eventually takes the shape of theinterior surface of the hydroforming mold. During the hydroformingprocess, the amount of metal per unit length of tube is varied. Morespecifically, as the linear exterior circumference is outwardlyexpanded, metal is replenished from the side portions so that the wallthickness can be maintained within ±10% of the original blank. In theareas of greatest expansion, the exterior circumference can be increasedby more than 16%, while the wall thickness is maintained within the ±10%range.

Strengthening of certain portions of a hydroformed tubular member can beaccomplished by expanding those portions more than others. The greaterthe expansion, the greater the amount of metal per unit length will beprovided, and the harder the metal will become.

The inventors of the present invention have contemplated use ofhydroforming to manufacture a seat back frame main vertical support. Thehydroforming technique is more cost effective than stamping, as a singletubular blank can be formed into a desired elongated integral tubularconfiguration, without welding or bending. In addition, because metal isstretched during the hydroforming process, it is mechanicallystrengthened, and less material needs to be used in forming the requireddiameter tubular structure.

However, as described above, in the hydroforming technique, the wallthickness remains relatively constant, even as the tubular blank isexpanded. Thus, while the hydroformed tube can be strengthened incertain areas by expansion, the process is limited in its ability toproduce a tubular member that has a greater wall thickness at certainareas, as is desirable in manufacturing a main vertical support for aseat back frame. While the entire main vertical support can be providedwith as great a wall thickness as desired throughout, an unnecessarilylarge amount of material would need to be used toward the upper portionsof the main vertical support to accommodate the desired thicknesstowards the lower portions.

There is thus a need to provide a seat frame assembly which overcomesall of the problems noted above. It is therefore an object of thepresent invention to meet this need. According to the present invention,there is provided a seat frame assembly for a motor vehicle comprising aseat frame and a seat back frame. The seat frame is constructed andarranged to have a seat cushion mounted thereon in overlying relation.The seat back frame is connected with the seat frame and has a pair ofspaced metallic vertical support portions at opposite sides thereof, theseat back frame constructed and arranged to have a seat back cushionmounted thereon. At least one of the vertical support portions areformed from a pair of telescoping tubular blanks including an elongatedinner metal blank formed into an integrally formed vertical member ofsaid at least one vertical portion extending from a lower portion of theseat back frame connected with the seat frame to an upper end of theseat back frame and a relatively shorter outer metal blank formed into asleeve rigidly secured in surrounding relation to the lower portion ofthe vertical support member. The outer blank and inner blank are formedinto the sleeve and the vertical member respectively during ahydroforming process in which the inner blank is expanded so that anouter surface thereof is moved into peripheral contact with an innersurface of the outer blank and the inner blank and the outer blank areexpanded into peripheral contact with die surfaces defining the exteriorsurfaces of the one vertical support portion.

It is a further object of the present invention to provide a method formanufacturing a seat frame assembly for a motor vehicle. The methodcomprises the steps of forming a seat frame adapted to support a seatcushion mounted thereon; forming a seat back frame having a pair ofspaced vertical tubular support portions at opposite sides thereof andadapted to support a seat back cushion mounted thereon, one of thevertical support portions having a generally greater weight and diameterthan the other and formed by 1) telescopingly moving a sleeve memberover one end portion of a metallic tubular member, 2) placing themetallic tubular member with the sleeve into a cavity of a die mold, thedie mold having an interior surface defining a shape of the cavity, 3)providing a fluid internally to the metallic tubular member withsufficient pressure so as to expand the tubular member outwardly so thatan exterior surface thereof at the one end portion is moved intoperipheral surface engagement with an interior surface of the sleeve,and so that other portions of the tubular member are moved intoengagement with the interior surface of the die mold to substantiallyconform the tubular member to the designed shape of the cavity.

It is understood that the benefits of accomplishing strength at thelower portions of the main vertical support are important irrespectiveof whether a reclining mechanism connects the seat frame with the seatback frame and whether a belt is attached to the main vertical support,due to the stresses present when an occupant is in the seat.

It is a further object of the present invention to provide an entireseat assembly which incorporates the seat frame assembly manufactured inaccordance with the principles of the present invention.

DETAILED DESCRIPTION

FIG. 1 is an exploded view showing a seat assembly manufactured inaccordance with the principles of the present invention.

FIG. 2 is an exploded view similar to the view in FIG. 1, but showingthe seat back frame detached from the seat frame.

FIG 3 is a perspective view showing the main vertical support member,together with sleeve of the present invention.

FIG. 4 is a cut-away sectional view taken along the line 4--4 in FIG. 3.

FIG. 5 is a perspective view, showing the main vertical support memberand sleeve of the present invention employed in a bench seat frameassembly.

FIGS. 6(A)-6(F) show method steps used in forming the vertical supportportion with the greater weight and diameter, including the verticalmain vertical support and sleeve, in accordance with the principles ofthe present invention.

FIG. 1 is an exploded view showing a seat assembly, generally indicatedat 10, manufactured in accordance with the principles of the presentinvention. The seat assembly includes a seat frame assembly, generallyindicated at 12, including a seat frame, generally indicated at 14, anda seat back frame, generally indicated at 16. Seat frame 14 includes apair of side brackets 18 (only one shown), and forward and rearwardtransverse brackets 20 (only the forward bracket being shown) forming asubstantially rectangular frame support. Mounted on the transverse andside brackets 20 and 18 is a pan-type frame member 22. It is to beunderstood that the present invention is not limited to this type ofseat frame, and that any type of seat frame can be provided.

The seat frame 14 is mounted on a mounting bracket 24, which is in turnmounted on a slide rail assembly, including a lower slide rail 26 andupper slide rail 27. The upper rail 27 is slidably mounted on the lowerrail 26 to permit the seat frame assembly to be forwardly and rearwardlyslidable into a desired position when mounted within a vehicle. A seatcushion 30 and seat back cushion 32 can be mounted in overlying relationon seat frame 14 and seat back frame 16, respectively.

The seat back frame 16 includes a pair of spaced vertical tubularsupport portions 34 at opposite sides thereof. As shown, one of thevertical tubular support portions 34 includes a main vertical supportmember 36, which has a generally greater weight and diameter than theopposite vertical support member 42.

A pair of horizontal support members, including an upper horizontalsupport 38 and lower horizontal support 40 interconnect the two tubularvertical support portions 34. As shown, it can be appreciated that oneor more of the horizontal supports may be integrally formed with thesmaller vertical support member 42. For example, in FIG. 1, the upperhorizontal support 38 is integrally formed with the opposite verticalsupport 42, while the lower horizontal support 40 is connected tovertical support 42, for example, by a welded or braised connection 44.The upper horizontal support 38 is provided with slots 39 adapted toreceive stem members 41 of a conventional headrest 43. Preferably, thehorizontal supports 38, 40 and vertical support 42 are formed by rollinga sheet of raw metal material into a tubular configuration, and thenseam welding.

As also shown in FIG. 1, the lower portion of main vertical supportmember 36 has an outer sleeve 46 rigidly secured in surrounding relationthereto. The outer sleeve 46 has an inner peripheral surface thereofdisposed in surface-to-surface contact with the outer peripheral surfaceof the lower portion of main vertical support member 36. The supportmember 36 is integrally formed from a single tubular blank during ahydroforming process, without the need to weld plural tubular membersend-to-end. The main vertical support member 36 and outer sleeve 46 arejoined to form a completed vertical support portion during thehydroforming process, which will be described in greater detail later.

Appropriate fasteners 50 pivotally connect rearward portions of the seatframe with lower portions of the seat back frame. The fasteners may beconsidered as forming part of a reclining assembly, including areclining mechanism generally indicated at 52, that operatively connectsrearward portions of the seat frame with lower portions of the seat backframe for pivotal movement. More particularly, the reclining mechanism52 rigidly connects the outer sleeve 46 and lower portion of mainvertical support member 36 with a rearward portion of one side of theseat frame. For example, in FIG. 1, the reclining mechanism 52 connectsouter sleeve 46 and lower portion of the main vertical support member 36with a rearward, left-hand side of the seat frame 14 from theperspective of a seat occupant. It can be appreciated, however, that ifthe main vertical support member 36 were to be provided at the rearwardright-hand side of the seat back frame 16, the reclining mechanism wouldthen be provided towards the rearward right-hand side of the seat frame14. The reclining mechanism 52 includes a manually movable handle 54which can be manually pivoted to unlatch a latching mechanism 51, showngenerally in dashed lines in FIG. 2, to enable the seat back frame 16 tobe pivotally movable with respect to the seat frame 14.

The seat frame assembly 12 is also provided with a seat belt assembly,including a belt retractor or reel 60 mounted on a rearward portion ofseat frame 14, in proximity with the lower portion of main verticalsupport member 36. The belt reel 60 can be of any conventional type.Fixed at the top portion of main vertical support member 36 is a beltguide 62 which receives belt 64 as it is pays out of belt reel 60. Thebelt extends from belt guide 62 downwardly in front of the seat backframe and terminates at anchor 66 fixed at the rearward left-handportion of side bracket 18. Intermediate the ends of belt 64 between thebelt guide 62 and end 66 is a conventional belt clasp 70 slidablydisposed along the belt and connectable with belt latch 72. Belt latch72 is fixed at an end of a second belt member 74 anchored at an oppositeend to a side bracket 18 in similar fashion to anchor 66. The clasp 70is received in belt latch 72 to thereby form belt 64 into a lap beltportion 76 and shoulder belt portion 78, as shown.

Referring now to FIG. 2, the seat back frame 16 is shown detached fromseat frame 14. As also shown, the vertical support portions 34 are eachprovided with bolt holes 80 for connection by fasteners 50 to seat frame14. The main vertical support 36 and sleeve 46 are also provided with asecond bolt hole 82 for connection with bolt hole 83 through rotatablearm 84 (shown in dashed lines) of reclining mechanism 52 with anappropriate fastener (not shown). Rotatable arm 84 is rotatable withrespect to the seat frame 14 when lever 54 is manually moved to permitthe seat back frame to be reclined.

FIG. 3 is a perspective view showing the main vertical support member36, together with sleeve 46 of the present invention. In FIG. 3, thesupport member has been turned 180 degrees from the view in FIG. 2, soas to show the surface 86 normally facing the opposite support member 42and not seen in FIG. 2. As shown, surface 86 is preferably provided withupper and lower openings 88 and 90, which are adapted to receive ends ofupper and lower horizontal supports 38 and 40, respectively. The endsare then seam welded in place within the openings. Alternatively,openings 88 and 90 can be omitted, and the ends of horizontal supportscan be welded or brazed as shown at connection 44 of the lowerhorizontal support with vertical support 42.

FIG. 4 is a cut-away sectional view taken along the line 4--4 in FIG. 3.As shown, the exterior peripheral surface 92 of the main verticalsupport 36 is in peripheral surface-to-surface contact with the innerperipheral surface 94 of sleeve 46.

FIG. 5 is a perspective view, showing the main vertical support member36 and sleeve 46 of the present invention employed in a bench seat frameassembly, generally indicated at 200. The bench seat frame assembly isnormally positioned as a back seat in a vehicle, and is adapted to carryplural passengers (e.g., up to four). The bench seat frame assemblyincludes a seat frame 202 and a seat back frame 204. Because the benchseat frame is longer than the seat shown in FIGS. 1 and 2, for addedsupport it is preferable to manufacture the seat back frame 204 with twomain vertical support members, one at each end, as shown. Each mainvertical support includes a belt guide 62 to accommodate respective seatbelt assemblies. While not shown in FIG. 5, the bench seat frameassembly 200 may be provided with up to two reclining mechanisms atopposite sides thereof to permit the seat back frame 204 to be pivotedrelative to the seat frame 202.

Referring now to FIGS. 6(A)-6(F), there is shown a method for formingthe vertical support portion with the greater weight and diameter,including the vertical main vertical support 36 and sleeve 46. As shownin FIG. 6(A), a tubular blank 300 is inserted between cooperating diehalves 302 and 304. The blank can be manufactured by any known process.Preferably, the blank can be formed by rolling a sheet of metallicmaterial into a complete closed tubular section and then seam-weldinglit. If desired, the tubular blank 300 can be pre-bent mechanicallybefore insertion into the hydroforming die, for example, by use ofmandrels in a CNC (computer numerically controlled) bending machine. Thepre-bending minimizes the amount of bending that must be accomplishedduring hydro-forming.

Before tubular blank 300 is placed in the die, a tubular outsert 320 (orouter blank) is telescopingly placed in surrounding relation over oneend of the tubular member that is to become the lower portion of themain vertical support member 36. During the hydroforming process, thetubular outsert will be formed into sleeve 46 disposed about the lowerportion of support member 36, as described hereinbefore.

After the tubular member 300 and outsert 320 are inserted into the die,hydroforming ports 308 are engaged with opposite ends 306 of the tubularstructure 300, and sealed thereto. As the die halves 302 and 304 aremoved towards one another, the tube 300 is slightly crushed, for exampleinto an oval cross-sectional shape, as shown in FIG. 6(D). The outsert320 may also be crushed in similar fashion.

Next, high pressure water, of up to 10,000 atmospheres is providedthrough the hydroforming ports 308 and into the inner confines oftubular structure 300. This high pressure causes the tubular structureto expand outwardly so that portions of outer surface 324 thereofsurrounded by outsert 320 are moved into peripheral engagement with theinner surface 322 of outsert 320, and other portions of outer surface324 are forced into peripheral engagement with the interior surface 310defining the cavity within the die. The expansion of blank 300 intoperipheral engagement with outsert 320 causes a corresponding expansionof outsert 320. Eventually, the tubular blank 300 and outsert 320substantially take a rectangular cross-sectional shape to conform to theinterior surface 310 of the die (e.g., see FIG. 6(F)).

As the high pressure fluid is provided into the tubular structure, it ispreferrable for hydroforming ports 308 to be forced inwardly against theopposite ends 306 of the blank to replenish the wall thickness of themetal as it expands into contact with the inner surface 310 of the die.The present invention contemplates, however, that the expansion can beaccomplished without pushing in the opposite ends of the of the blank.Where the opposite ends are not inwardly pushed to replenish the metal,expansion should be limited to 5%. Expansion more than this amountwithout replenishing metal from the side portions of the blank may causean excessive reduction in wall thickness.

If desired, openings 88 and 90 shown in FIG. 3 for receiving horizontalcross members 38 and 40 can be formed during the hydroforming process byproviding vent ports at portions in the molding die at which theopenings are to be formed, and momentarily opening the vent ports toblow holes through the tubular structure.

It can be appreciated that during the aforementioned hydroformingprocess, the amount of metal per unit length of tube is varied. Morespecifically, as the linear exterior circumference is outwardlyexpanded, metal is replenished from the side portions so that the wallthickness is maintained within ±10% of the original blank. In the areasof greatest expansion, the exterior circumference is increased by morethan 16%, while the wall thickness is maintained within the ±10% range.

In FIG. 6(E), it can be seen that the ends 306 are deformed as a resultof the hydroforming process. Preferably, these end are cut off in asubsequent process before the hydroformed assembly is incorporated intoa seat frame assembly.

The hydroforming molding technique employed herein is disclosed ingreater detail, for example, in "Industrieanzeiger" No. 20 of 9, Mar.1984; and "Metallumformtechnik"Issue 1D/91, zp. 15 ff: A. Ebbinghaus:"Precision Workpieces in Light Construction, Manufactured ThroughInternal High Pressure Mouldings"; and "Werkstatt und Betrieb" 123(1990), 3, P. 241-243: A. Ebbinghaus: "Economic Construction withInternal High Pressure Moulded Precision Workpieces": and "Werkstatt undBetrieb" 122 (1991), 11 (1989), P. 933-938, the above publications beingfully incorporated herein by reference.

While the invention has been illustrated and described in detail in thedrawings and foregoing description, the same is to be considered asillustrative and not limiting in character, it being understood that thepreferred embodiment has been shown and described and that all changesand modifications that come within the spirit and scope of the appendedclaims are to be protected.

What is claimed is:
 1. A seat frame assembly for a motor vehiclecomprising:a seat frame constructed and arranged to enable a seatcushion to be mounted thereon in overlying relation with respectthereto; a seat back frame connected with said seat frame and having apair of spaced metallic vertical support portions at opposite sidesthereof, said seat back frame constructed and arranged to enable a seatback cushion to be mounted thereon, at least one of said verticalsupport portions comprising an integrally formed elongated verticalmember extending from a lower portion thereof connected with said seatframe to an upper portion thereof terminating generally at an upper endof said seat back frame, and a sleeve relatively shorter than thevertical member and rigidly secured in surrounding relation to saidlower portion of said vertical member, said vertical member and saidsleeve being formed from a pair of telescoping tubular blanks includingan elongated inner metal blank and an outer blank shorter than the innerblank, said outer blank and inner blank being formed into said sleeveand said vertical member respectively during a hydroforming process inwhich said inner blank is expanded so that an outer surface thereof ismoved into peripheral contact with an inner surface of said outer blankand in which said inner blank and said outer blank are expanded togetherso that the outer blank is moved into peripheral contact with diesurfaces defining an exterior configuration of said at least onevertical support portion.
 2. A seat frame assembly according to claim 1,further comprising a reclining mechanism operatively connecting rearwardportions of said seat frame with lower portions of said seat back frameto enable said seat back frame to be pivotally movable with respect tosaid seat frame, said reclining mechanism rigidly connecting, on oneside of the seat frame assembly, said seat frame with the sleeve andlower portion of said vertical member.
 3. A seat frame assemblyaccording to claim 1, further comprising a seat belt assembly includingaseat belt reel fixed to said seat frame assembly, a belt guide fixed atan upper end of said vertical member on one side of the seat frameassembly, a main belt paying outwardly from said belt reel at one endand extending upwardly therefrom through said belt guide, said main beltextending downwardly from said belt guide and having an opposite endanchored to said seat frame on said one side of the seat frame assembly,a belt clasp associated with said main belt and disposed thereon inslidably movable relation between said belt guide and said opposite endof the main belt, a second belt anchored at one end to said seat frameat a side of the seat frame assembly opposite said one side and havingan opposite end, a belt latch associated with said opposite end of saidsecond belt and adapted to receive said belt clasp in latchingengagement.
 4. A seat frame assembly according to claim 1, furthercomprising upper and lower horizontal supports interconnected betweensaid spaced vertical support portions.
 5. A seat frame assemblyaccording to claim 4, wherein said spaced vertical support portionscomprise respective outer surfaces facing one another, said outersurfaces having upper and lower openings formed therein for receivingsaid upper and lower horizontal supports, and wherein said upper andlower horizontal supports are welded to edges defining said upper andlower openings.
 6. A seat frame assembly according to claim 4, whereinsaid upper horizontal support is integrally formed with one of saidvertical support portions.
 7. The invention according to claim 1,wherein said seat frame assembly comprises a bench seat frame assemblywherein each of said spaced metallic vertical support portionsrespectively comprises 1) one said integrally formed elongate verticalmember extending from the lower portion thereof connected with said seatframe to the upper portion thereof terminating generally at the upperend of the seat back frame, and 2) one said sleeve relatively shorterthan the vertical member and rigidly secured in surrounding relation tothe lower portion of the vertical member,each said vertical supportportion having said elongate vertical member and said sleeve thereofformed from a pair of telescoping tubular blanks including 1) anelongated inner metal blank which is to be formed into said integrallyformed vertical member, and 2) an outer metal blank shorter than theinner blank and formed into said sleeve rigidly secured in surroundingrelation to said lower portion of said vertical member, each saidvertical support portion having said sleeve and said vertical memberthereof formed from said outer blank and inner blank respectively duringa hydroforming process in which said inner blank is expanded so that anouter surface thereof is moved into peripheral contact with an innersurface of said outer blank and in which said inner blank and said outerblank are expanded together so that the outer blank is moved intoperipheral contact with die surfaces defining an exterior configurationof the associated vertical support portion.
 8. A seat frame assemblyaccording to claim 7, further comprising a pair of seat belt assemblies,each includinga seat belt reel fixed at one side of said seat frameassembly, a belt guide fixed at an upper end of an associated one ofsaid vertical support members, a main belt paying outwardly from saidbelt reel at one end thereof and extending upwardly therefrom throughsaid belt guide, said main belt extending downwardly from said beltguide and having an opposite end anchored to a side of said seat frameadjacent said associated one of said vertical support members, a beltclasp associated with said main belt and disposed thereon in slidablymovable relation between said belt guide and said opposite end of themain belt, a second belt anchored to said seat frame at a position onthe seat frame laterally spaced from the position at which the main beltis anchored and having an opposite end, a belt latch associated withsaid opposite end of said second belt constructed and arranged toreceive said belt clasp in latching engagement.
 9. A seat frame assemblyaccording to claim 8, further comprising upper and lower horizontalsupports interconnected between said spaced vertical support portions.10. A seat assembly for a motor vehicle comprising:a seat frame; a seatcushion mounted on said seat frame; a seat back frame connected withsaid seat frame; a seat back cushion mounted on said seat back frame;said seat back frame having a pair of spaced metallic vertical supportportions at opposite sides thereof, at least one of said verticalsupport portions comprising an integrally formed elongate verticalmember extending from a lower portion thereof connected with said seatframe to an upper portion thereof terminating generally at an upper endof said seat back frame, and a sleeve relatively shorter than thevertical member and rigidly secured in surrounding relation to saidlower portion of said vertical member, said vertical member and saidsleeve being formed from a pair of telescoping tubular blanks includingan elongated inner metal blank and an outer blank shorter than the innerblank, said outer blank and inner blank being formed into said sleeveand said vertical member respectively during a hydroforming process inwhich said inner blank is expanded so that an outer surface thereof ismoved into peripheral contact with an inner surface of said outer blankand in which said inner blank and said outer blank are then expandedtogether so that the outer blank is moved into peripheral contact withdie surfaces defining an exterior configuration of said at least onevertical support portion.
 11. A seat assembly according to claim 10,further comprising a reclining mechanism operatively connecting rearwardportions of said seat frame with lower portions of said seat back frameto enable said seat back frame to be pivotally movable with respect tosaid seat frame, said reclining mechanism rigidly connecting, on oneside of the seat frame assembly, said seat frame with the sleeve andlower portion of said vertical member.
 12. A seat assembly according toclaim 11, further comprising a seat belt assembly includinga seat beltreel fixed to a rearward portion of said seat frame, a belt guide fixedat an upper end of said vertical support member, a main belt payingoutwardly from said belt reel at one end and extending upwardlytherefrom through said belt guide, said main belt extending downwardlyfrom said belt guide and anchored to a side of said seat frame atanother end, a belt clasp associated with said main belt and disposedthereon in slidably movable relation between said belt guide and saidend at which the main belt is anchored to said seat frame, a second beltanchored at one end to said seat frame at a side opposite the side atwhich said the main belt is anchored and having an opposite end, a beltlatch associated with said opposite end of said second belt and adaptedto receive said belt clasp in latching engagement.
 13. A seat assemblyaccording to claim 10, further comprising upper and lower horizontalsupport members interconnected between said spaced vertical supportportions.
 14. A seat assembly according to claim 13, wherein saidvertical support portions comprise respective outer surface facing oneanother, said outer surfaces having upper and lower openings formedtherein for receiving said upper and lower horizontal supports, andwherein said upper and lower horizontal supports are welded to edgesdefining said upper and lower openings.
 15. A seat assembly according toclaim 13, wherein said upper horizontal support is integrally formedwith one of said vertical support portions.